[FFmpeg-devel] [PATCH] dashenc: Write out DASH manifest immediately in streaming mode

[Timo Rothenpieler]

On 08.06.2021 21:24, Kevin LaFlamme wrote:
> For streaming mode with fragmented MP4 the intention is to have the client read a partial file since it’s broken up into sequential boxes that are playable independently. This doesn’t change the segment files themselves or how they are written, it just writes a full index file ahead of time.
> 
> Even currently, the manifest gets written after the first segment is written and the player can immediately attempt to start reading the second segment before it’s fully written.
> 
> This is the same thing that the “-lhls” is doing in the block below, writing out the HLS manifest immediately so that it contains X-EXT-PREFETCH fields for the partial segment files.
> 
> Currently, if you have a low latency DASH stream with “-ldash” and “-streaming” and the player joins in the middle of the stream everything works and it starts playing from the middle of the current segment. This means even with 10 second segments you can have latency < 1sec of the live edge. However, this doesn’t work for the very first segment because the manifest isn’t available to the player yet.
> 
> I have a low-latency player where I’m seeing this issue right now and this addresses the problem, and seems consistent with the “-lhls” handling below, but happy to make changes if there is something else I’m missing.

Yes, I'm aware that that's how it's supposed to work in theory.
But does that work with any HTTP server?
Do they really manage to stream the file while it's being written to?
Or does this need special software to serve the file? And in turn, will 
it break for a user just pointing apache/nginx at such a list?

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